Copper multicomponent alloy and its use

ABSTRACT

The invention relates to a copper multicomponent alloy, consisting of [in % by weight]: 
                                       Ni   1.0 to 15.0%         Sn   2.0 to 12.0%         Mn   0.1 to 5.0%         Si   0.1 to 3.0%,                                  
remainder Cu and inevitable impurities,
     optionally individually or in combination up to 1.5% Ti, Co, Cr, Al, Fe, Zn, Sb,   optionally individually or in combination up to 0.5% B, Zr, P, S,   optionally up to 25% Pb.

The invention relates to a copper multicomponent alloy and its use.

Wrought alloys based on copper-nickel-tin have long been known. By way of example, patent U.S. Pat. No. 1,535,542 describes an alloy of this type with a view to improving materials properties in terms of the resistance to corrosion, the ductility and the formability.

Patent U.S. Pat. No. 1,816,509 also discloses a copper-nickel-tin alloy as well as a process for the further treatment of alloys of this type. After the alloy has been cast, the process includes a cold-forming process and, to set particular materials properties, a heat treatment to homogenize and age-harden the alloy. The heat treatment leads to the formation of continuous and discontinuous precipitations together with the formation of a further γ-phase.

Document DE 41 21 994 C2 has disclosed a further process, in which a copper-nickel-tin alloy for sliding element applications, as a wrought alloy, passes through standard casting and forming steps, wherein after the final cold-forming operation the γ-phase is formed as continuous and discontinuous precipitations as a result of a heat treatment. The proportion formed by the γ-phase by volume is dependent on the procedure selected for the heat treatment.

Subsequently, numerous tests have been carried out on the copper-nickel-tin alloy system (U.S. Pat. No. 4,142,918, U.S. Pat. No. 4,406,712 and WO 2005/108631 A1), in order to continuously further develop the materials properties. However, in practice it has been found that some combinations of properties, such as for example the wear resistance and the hot strength, cannot be simultaneously optimized using known process engineering. An improvement in one materials property is to the detriment of another property which is equally important for certain application areas.

Therefore, the invention is based on the object of developing a copper multicomponent alloy in such a manner as to achieve both a high mechanical wear resistance and a high hot strength.

In terms of a copper multicomponent alloy, the invention is represented by the features of Claim 1, while its use is represented by the features of Claim 7. The further, dependent claims relate to advantageous refinements and developments of the invention.

The invention encompasses a copper multicomponent alloy, consisting of [in % by weight]:

Ni 1.0 to 15.0% Sn 2.0 to 12.0% Mn 0.1 to 5.0% Si 0.1 to 3.0%, remainder Cu and inevitable impurities,

-   optionally individually or in combination up to 1.5% Ti, Co, Cr, Al,     Fe, Zn, Sb, -   optionally individually or in combination up to 0.5% B, Zr, P, S, -   optionally up to 25% Pb.

The invention is based on the consideration of specifying a copper multicomponent alloy which simultaneously offers a very good wear resistance and, in particular when used as a sliding element in thermally stressed environs, an excellent hot strength. However, if the silicon and/or manganese content exceed the indicated maximum levels of 3% by weight and 5% by weight, respectively, difficulties are likely to be encountered in further processing, in particular on account of cracks in the edges of the strip material during rolling. Addition of the elements Ti, Co, Cr and Fe serve to form further silicide phases. Sb and Al can be added on account of the resultant improvement in the sliding properties and/or the corrosion resistance. The further elements B, Zr, P and S serve to deoxidize the melt or make a contribution to grain refining. The element lead is connected to the production of cast alloys.

The wrought Cu—Ni—Sn alloys according to the invention are spinodally segregating systems which are particularly suitable for use as bearing materials in engine construction as a solid material and in composite sliding elements. These materials have good frictional and wearing properties as well as a good resistance to corrosion. The thermal stability is also excellent.

Degrees of cold-forming of up to 60% can be achieved in these materials with Ni contents of from 1 to 15% by weight and Sn contents of from 2 to 12% by weight. In combination with soft-annealing, it is possible to produce thin strips which are suitable for material composites. These alloys can also be age-hardened in the temperature range between 300 and 500° C. This leads to work-hardening of the material on account of the spinodal segregation which occurs. Moreover, continuous and/or discontinuous precipitations may form. This form of precipitation hardening is significantly superior to binary copper-based alloys.

The advantages achieved by the invention compared to binary copper-based alloys and conventional Cu—Ni—Sn alloys are in particular that the materials properties can be optimally matched to the particular requirements by means of rolling, homogenization annealing and age-hardening. By way of example, it is also possible for a softer or harder copper multicomponent alloy layer to be combined with harder materials, for example steel, in composite sliding elements by means of mechanical and thermal treatment.

In a particularly preferred configuration of the invention, the copper multicomponent alloy may contain up to 2.5% by weight Mn and up to 1.5% by weight Si. It has been found that modified Cu—Ni—Sn variants with an Si content of up to 1.5% by weight and an Mn content of up to 2.5% by weight can be manufactured with improved materials properties. Further laboratory tests have likewise already been carried out in this respect and the limit values have been confirmed.

This pursues the objective of further improving the wear resistance of Cu—Ni—Sn alloys by forming hard intermetallic phases. These further hard-material phases are manganese-nickel silicides. Cu—Ni—Sn alloys already have very good properties in terms of the sliding properties, resistance to corrosion and resistance to relaxation at room temperature. The hard phases which are formed reduce the susceptibility to adhesion in the mixed friction range and further increase the hot strength and ductility at elevated temperatures.

Surprisingly, by combining the microstructural constituents which contribute to wear resistance with a spinodally segregating alloy of the Cu—Ni—Sn system, it is possible on the one hand to reduce the run-in requirements resulting from wear at the start of the application of stresses and on the other hand a Cu—Ni—Sn—Mn—Si material of this type also proves to have a good hot strength and a sufficient ductility.

The copper multicomponent alloy may advantageously contain up to 1.6% by weight Mn and up to 0.7% by weight Si. In particular, it has been ensured that manufacturing is actually possible from a production engineering perspective at an Si content of up to 0.7% by weight and an Mn content of up to 1.6% by weight. In the event of higher silicon and manganese contents, suitable adjustments within the scope of standard measures should be implemented with regard to the casting parameters.

The copper multicomponent alloy may advantageously undergo at least one heat treatment at 300 to 500° C. In the process, the material is work-hardened as a result of the spinodal segregation which takes place.

In a preferred configuration of the invention, the copper multicomponent alloy may undergo at least one heat treatment at 600 to 800° C. The heat treatment in this range results in homogenization making the material more ductile.

In a particularly preferred configuration of the invention, the copper multicomponent alloy may undergo a combination of at least one solution anneal at 600 to 800° C. and at least one age-hardening treatment at 300 to 500° C. In the process, the material is work-hardened as a result of the spinodal segregation which takes place. The heat treatment in this range leads to homogenization, as a result of which the material becomes softer. The materials properties of the copper multicomponent alloy can be optimally matched to the particular requirements by means of a homogenization anneal and the hardening of the material which takes place during age-hardening or rolling.

In a further preferred configuration, the copper multicomponent alloy can be used for sliding elements or plug connectors.

Exemplary embodiments of the invention are explained in more detail on the basis of the following example and the scanning electron microscope image shown in FIG. 1.

EXAMPLE

In series of tests, ingots with different Mn—Si ratios were cast and then cold-worked further. The alloy variants tested are summarized in Table 1. The cast ingots were homogenized in the temperature range between 700 and 800° C. and then milled. Strips with thicknesses of between 2.5 and 2.85 mm were produced by a plurality of cold-forming stages and intermediate annealing steps. The strips were cold-rolled and annealed in the temperature range between 700 and 800° C. in order to achieve sufficient cold-formability.

TABLE 1 Cu Ni Sn Mn Si Cu − [% by [% by [% by [% by [% by Ni − Sn + Mn + Si weight) weight] weight] weight] weight] Variant 1 Remainder 5.6–6.0 5.2–5.6 1.7–2.0 0.2–0.3 Variant 2 Remainder 5.6–6.0 5.2–5.6 1.3–1.6 0.2–0.3 Variant 3 Remainder 5.6–6.0 5.2–5.6 1.3–1.6 0.5–0.7 Variant 4 Remainder 5.6–6.0 5.2–5.6 0.8–1.0 0.1–0.3 Variant 5 Remainder 5.6–6.0 5.2–5.6 0.8–1.0 0.3–0.5 Variant 6 Remainder 5.6–6.0 5.2–5.6 0.4–0.6 0.4–0.6 Variant 7 Remainder 5.6–6.0 5.2–5.6 0.9–1.1 0.9–1.1 Variant 8 Remainder 5.6–6.0 5.2–5.6 1.8–2.1 0.5–0.6 Variant 9 Remainder 5.6–6.0 5.2–5.6 1.8–2.1 0.9–1.1

As expected, it was confirmed that the cold-formability of the Cu—Ni—Sn alloy modified with silicides is slightly lower than in the case of a Cu—Ni—Sn alloy without further silicide phases.

In a further process step, strips of this type can be combined to form a strong material composite by roll-cladding processes. Silicide-modified Cu—Ni—Sn alloys also have a significantly lower coefficient of friction than the silicide-free variant. The alloy according to the invention is therefore particularly suitable as a primary material for use as a sliding element (liners, thrust washers, etc.) in the automotive industry for engines, transmissions and hydraulics.

FIG. 1 shows a scanning electron microscopy image of the surface of a copper multicomponent alloy. The relatively finely distributed manganese-nickel silicides 2, which are embedded in the alloy matrix 1, can be clearly seen. These silicides are formed as the first precipitation in the melt in a temperature range as early as around 1100° C. If the melt composition is selected appropriately, the available silicon and manganese are precipitated together with a nickel content which is present in excess to form the silicide. The nickel content consumed in the silicide can be suitably taken into account for the subsequent formation of the matrix by using a higher nickel content in the melt.

The composition of the silicides does not necessarily have to correspond to a predetermined stoichiometry. Depending on the procedure adopted, determined in particular by the cooling rate, ternary intermetallic phases precipitate in the form of the silicides of type (Mn, Ni)_(x)Si, which are in the range between the binary boundary phases Mn₅Si₃ and Ni₂Si.

The mechanical properties of strips of the silicide-containing copper multicomponent alloy, in the as-rolled state, had a tensile strength Rm of 560 MPa and a yield strength of 480 MPa with an elongation at break A5 of 25%. The hardness HB was approx. 176.

After age-hardening of the strips, a tensile strength Rm of 715 MPa and a yield strength Rp_(0.2) of 630 MPa with an elongation at break A5 of 17% were determined. The hardness HB was approx. 235. 

1. Copper multicomponent alloy, consisting of [in % by weight]: Ni 1.0 to 15.0% Sn 2.0 to 12.0% Mn 0.1 to 5.0% Si 0.1 to 3.0%,

remainder Cu and inevitable impurities, optionally individually or in combination up to 1.5% Ti, Co, Cr, Al, Fe, Zn, Sb, optionally individually or in combination up to 0.5% B, Zr, P, S, optionally up to 25% Pb.
 2. Copper multicomponent alloy according to claim 1, characterized in that it contains up to 2.5% Mn and up to 1.5% Si.
 3. Copper multicomponent alloy according to claim 2, characterized in that it contains up to 1.6% Mn and up to 0.7% Si.
 4. Copper multicomponent alloy according to claim 1, characterized in that it has undergone at least one heat treatment at 300 to 500° C.
 5. Copper multicomponent alloy according to claim 1, characterized in that it has undergone at least one heat treatment at 600 to 800° C.
 6. Copper multicomponent alloy according to claim 1, characterized in that it has undergone a combination of at least one solution anneal at 600 to 800° C. and at least one age-hardening treatment at 300 to 500° C.
 7. Use of the copper multicomponent alloy according to claim 1 for sliding elements or plug connectors. 